In the manufacture of unpackaged semiconductor dice it is sometimes necessary to make an electrical connection with the bond pads of the dice for testing or other purposes. For example, burn-in and full functionality tests are used to certify each unpackaged die as a known good die (KGD). During the test procedures test apparatus for a single bare die (also referred to as carriers) take the place of conventional plastic or ceramic semiconductor packages. Exemplary test apparatus are disclosed in U.S. Pat. Nos. 5,302,891; 5,408,190 and 5,495,179 to Wood et al.
This type of test apparatus typically includes an interconnect component for making the temporary electrical connection between the die and test apparatus. For example, U.S. Pat. No. 5,483,741 to Akram et al. discloses a method for fabricating an interconnect with silicon contact members.
Another type of interconnect for these test apparatus is formed with microbump contact members. For example, U.S. Pat. No. 5,487,999 to Farnworth discloses an interconnect for bare dice that includes microbump contact members. Microbump interconnects can be fabricated using TAB tape developed for tape automated bonding of semiconductor dice. This type of TAB tape is sold by Nitto Denko America, Inc. under the trademark ASMATTM.
The microbump contact members comprise metal bumps formed on an insulative polyimide film. The microbumps can be formed on metal filled vias using an electroplating process. In addition, conductive traces formed of patterned metal foil are also mounted to the polyimide film to establish a circuit path to the microbumps. For forming an interconnect for testing bare dice, the polyimide film with the microbumps and conductive traces thereon, can be mounted to a rigid substrate.
With this type of microbump interconnect, the manufacturing process for the microbumps is complicated and requires specialized manufacturing equipment. Following the microbump manufacturing process, the polyimide film must be cut to shape and mounted on the substrate. This can also be a complicated and tedious process. In particular, the polyimide film is fragile and difficult to cut and attach to the rigid substrate. In addition, an adhesive layer must be formed between the polyimide film and the rigid substrate. The thickness and compressive properties of this adhesive layer can have a profound effect on the function of the microbump interconnect. Accordingly, undesirable variables can be introduced by the steps and materials used during the substrate mounting process.
The present invention is directed to a simplified method for forming microbump interconnects directly on a rigid substrate. This eliminates a separate substrate mounting step for the microbumps. In addition, fabrication of the microbumps is simplified and an improved low resistance microbump structure is provided.
In view of the foregoing, it is an object of the present invention to provide an improved method for forming a microbump interconnect for bare semiconductor dice.
It is a further object of the invention to provide an improved method for forming a microbump interconnect having a rigid substrate and low resistance microbumps formed on a flexible compliant layer.
It is yet another object of the present invention to provide an improved microbump interconnect useful for making a temporary or permanent electrical connection to a bare semiconductor die.
It is a still further object of the present invention to provide an improved microbump interconnect that can be used in a test apparatus for testing bare dice or that can be used for flip chip mounting semiconductor dice to form multi chip modules and other electronic devices.
Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds.